Process for the production of a waterbearing explosive composition

ABSTRACT

A PROCESS FOR THE PRODUCTION OF A WATER-BEARING EXPLOSIVE COMPOSITION, WHEREIN A PREVIOUSLY PREPARED, THICKENED SOLUTION OR DISPERSION SUBSTANTIALLY COMPRISING THE OXIDIZING COMPONENTS OF THE EXPLOSIVE COMPOSITION, IS MIXED WITH THE COMBUSTIBLE OR OXYGEN CONSUMING COMPONENTS OF THE EXPLOSIVE COMPOSITION, CHARACTERIZED THEREIN THAT ALSO THE OXYGEN CONSUMING COMPONENTS ARE USED IN THE FORM OF A VISCOUS OR THICKENED SOLUTION OR DISPERSION HAVING NEARLY THE SAME CONSISTENCY AS THE OXIDIZING COMPONENT MIXTURE.

" United States Patent 3,834,954 PROCESS FOR THE PRODUCTION OF A WATER-BEARING EXPLOSIVE COMPOSITION Eirik Samuelsen, Lierbyen, Norway,assignor to Dyno Induslrier A.S., Oslo, Norway No Drawing. Filed Mar. 2,1972, Ser. No. 231,376 Claims priority, application Norway, Mar. 10,1971, 907

Int. Cl. C06b 1/04 US. Cl. 149-2 11 Claims ABSTRACT OF THE DISCLOSUREThe present invention relates to the production of explosives whichcomprise a water-bearing mixture of oxidizing salts and fuel componentsof various kinds, constituting a viscous dispersion of solid particlesin a thickened aqueous medium.

At present, explosives of the stated nature are produced in two clearlydifferent ways, viz., either in a manufacturing plant production of thecomplete explosive composition, which not till after a contingentstorage and subsequent transport to the blasting site is placed in theborehole, or in the way that the components of the explosive, optionallyin the form of certain premixtures or prepared solutions, are mixed onthe site immediately in connection with the pumping of the explosiveinto the bore-holes.

The first mentioned method comprises the practice of preparing loadingunits, cartridges, preferably in plastic tubing, of dimensions adaptedto the bore-holes in which they are to be used, as well as the practiceof storing and transporting the material in essentially larger units ortransport containers, from which the explosive is unloaded or pumpedinto the bore-holes.

This method is advantageous in that the composition of the explosive andthe specifications thereof may be supervised more readily and be checkedbefore use. A certain disadvantage consists therein that during storagethe explosive may be subject to changes in an unfavourable directionthat concerns its blasting qualities as well as its consistency. Thelatter may be of essential importance to a rational and proper operationof the pumping and loading on the place of use. Another disadvantage ofthe manufacturing plant production method is that the entire amount ofexplosive is present as a detonating explosive during storage andtransport, with the corresponding safety rules.

The second method generally has the distinct advantage that duringtransport and storage no complete detonating explosive exists, sincethis is established only in the immediate vicinity of the bore-holes inwhich to be used, and immediately before it is loaded therein. This isentirely the fact when none of the components has any explosivecharacter per se, and even if that is the case, the amount thereof,being subject to specific transporting and storing restrictions, will besubstantially less than if the first mentioned method comprising plantproduction had been used.

However, the last mentioned method, comprising production on the site,has the disadvantage that the composition of the explosive andconsequently its properties, is dependent on a carefully and accuratelyperformed metering and mixing operation on the site. Up to now the3,834,954 Patented Sept. 10, 1974 method has been characterized thereinthat at least one of the flow of materials to the mixing operation hasbeen a particulate solid material, mostly the fuel components of theexplosive, and often also a part of the oxidizing salts, preferablyammonium nitrate has been fed to the mixing operation as a solidsubstance. The other quantities of salts and other water solublecomponents of the explosive then have constituted a solution which isincluded in the mixing operation as a readily pumpable flow of material.

It is not easy to perform an accurate metering of dry components instrictly specified ratios into a flow of liquid. It is particularlydifficult when the dry components are very finely pulverized, as in thatcase both their bulk densities and flow properties are stronglydependent on the air content of the particulate material as well as ofthe other properties of the powder particles. Especially for explosivesof the herein disclosed nature it is of great importance that the drycomponents are very finely pulverised, and it has often been necessaryto take different measures, such as vibrating of hopperwalls, mechanicalagitating devices inside the hoppers, or blowing air into the hoppers tocounteract failure in the feeding of the dry components through screwconveyors or other metering devices. Under unfavourable conditions, suchas high humidity in the air or high temperature, the particulatematerial has demonstrated such a tendency to sintering and formation oflumps that even the measures mentioned above have not been able toensure the required result in metering the material.

The object of the present invention is to obtain the advantage of thelast mentioned method as far as concerns the final explosive to beestablished immediately before use on the site, at the same time as thedisadvantages of handling and accurate metering of the dry particulatecomponents are eliminated.

The invention consists therein that the nature and amount of thecomponents of the explosive are selected such that it may be prepared atthe place of use by simple mixing of two in principle liquid, viscous orpasty, volumetrically readily metered component mixtures, the one ofwhich in a per se known way essentially comprises an aqueous solution ordispersion of oxidizing salts, the second component mixture essentiallycomprising the fuel components.

The essential feature of the invention, thus, consists in letting thefuel components of the explosive be introduced into the final mixingoperation in a pumpable form. In such a viscous or pasty componentmixture a liquid phase should be included which is mixable with the saltsolution constituting the liquid phase of the other pumpable componentmixture. As a suitable dispergent medium for different solid fuelcomponents several liquid media have been found, having in common thatthey consist entirely or substantially of combustible materials, andthat they have a relatively high viscosity which prevents insoluble fuelparticles from sedimentation. As examples of such suitable dispersingliquids for solid fuel components may be mentioned ethyleneglycolthickened with small amounts of specific thickening agents, such asPolyhall, Grade 295, supplied by the firm Mayhall, Switzerland orKelsan, supplied by Kelco C0,, U.S.A. and, further, molasses andevaporated sulfite liquor from a sulfite pulping process.

Among the combustible components to be dispersed in such a liquid theremust generally be at least one to provide the final explosive mixturewith a necessary degree of sensitivity toward initiation. Of suchsensitizing agents primarily either a solid substance having explosivecharacter, preferably trinitro toluene, or finely divided, preferablyflaked aluminium comes into question. It is a feature of the inventionthat the initiability of these sensitizing agents will be considerablyreduced by being dispersed in a liquid phase, while they are, however,provid ing the final explosive mixture in which also the oxidizing saltsare present, with a sufficient sensitivity towards initiation.

In addition to these sensitizing agents the viscous or pasty componentmixture may comprise various other combustible substances, which bytaking part in the reaction contribute to the generation of heat andcombustion gases. One group of such combustible substances comprisespowders of coal, asphalt, pitch, peat, wood, cork, bark, and the like,another group comprising powders of metals such as aluminium, magnesium,silicon, boron or alloys thereof.

Beside these components which constitute essential constituents of thefinal explosive, the fuel component mixture as well as the mixture ofthe oxidizing salts may comprise constituents which influence orstabilize the consistency of both component mixtures or of the finalexplosive composition, such as, e.g., thickening agents and crosslinkingagents for these thickening agents, or, which influence or stabilize thecontent of dispersed air in the mixtures, such as dispersing agents orother surfactant agents. Such substances may also be introducedseparately during the final mixing operation, in case this is foundadvantageous.

In the practice of the present invention it is of importance, primarily,to perform an accurate metering of both component mixtures, and,secondarily, a thorough blending thereof.

It is a feature of the invention that the volumetric metering of thecomponent mixtures is far more easy to perform accurately andreproducibly than metering of dry components as practiced previously. Asa suitable pumping means, preferably, gear pumps of different designwill come into question. Moreover, a preferred means is an arrangementin which two gear pumps, one for each of the component mixtures, aredriven by the same motor, and wherein the ratio between the speeds ofthe pumps may be varied for controlling the required mixing ratio, whilethe production rate of the final explosive may be varied by means of aspeed variator for the motor in common. An alternative arrangementconsists in pumping one component mixture with varying speed, allowing aflow meter in this flow of material to control the pump speed in thesecond fiow of material in an adjustable, though stable condition undervarying pump speeds. Such arrangements are suitable both for themaintenance of the correct composition of the explosive and for adaptingthe production rate of the loading operation and other conditions on thesite.

Irrespective of the pumping means being selected for an accurate andstable metering of both component mixtures in a determined ratio, thefinal mixing of these two materials must be completed before theexplosive is introduced into the bore hole. This final mixing may befacilitated by suitable construction of the part where the flows ofmaterial are combined, e.g., by causing one flow of material to flowthrough a nozzle having a large number of openings, into the second flowof material. After this combination of the component mixtures theyshould be thoroughly blended. This may be achieved by means ofmechanically operated mixing means, such as paddles or stirring bladesoperating in a mixing chamber, but a preferred embodiment of this mixingoperation comprises the use of a so called static mixer, in which thetotal flow of material is split up and caused to change directionseveral times, only as a consequence of the flow movement in the twocomponent mixtures originally effected by the pumps.

Irrespective of the mixing technique used, it has been found suitablethat the two component mixtures are of substantially the same viscosityor consistency, thereby reducing essentially the risk that one of thecomponent mixtures be present as non-dispersed lumps or localinhomogenities in the remaining mixture.

In the following there will be given an example of an emobidment of theinvention, however, it will ppear from the foregoing that the inventionis not limited to this example, but that it includes every production ofaqueous explosives in which two viscous or pasty component mixtures arecombined to form the final explosives.

EXAMPLE 1 Component mixture A A viscous up to pasty dispersion ofoxiding salts is prepared having the following composition, in parts byweight:

Parts Ammonium nitrate 40 Nitrate of lime, fertilizer grade 45 Sodiumnitrates 4 Urea 5 Water 4 Ethylene glycol 1.5 Tapioca starch 0.4 GuarGum 0.1

Total 100.0

Remark: The nitrate of lime used contains about 79% calcium nitrate, 6%ammonium nitrate and 15% water.

The first five components are heated under stirring to about 65 C.,whereafter the two last mentioned components, the thickening agents, aredispersed in the ethylene glycol and added to the salt solution. Coolingunder stirring causes initial salt precipitation at about 30 C., whereasthe component mixture maintains its pumpability and character of aviscous dispersion down to between 10 C. and 20 C. By decomposition,this component mixture will during detonation place about 210 grams ofoxygen per kilogram, at the disposal for the combustion of othersubstances.

Component mixture B A viscous mixture of combustible components areproduced having the following composition, in parts by weight:

Parts Ethylene glycol 72.2 Thickening agent Polyhall 295 0.4 Aluminium,flake form 18.0 Asphalt powder 9.4

Total 100.0

The thickening agent is dispersed in the glycol, which is heated toabout 80 C., thereby producing a clear solution which after cooling hasa viscosity of about 2000 cps. -In this solution the two last mentionedcomponents are then dispersed. This component mixture needs about 1400grams of oxygen per kilogram for complete combustion.

Preparation of the explosive When admixing 87 parts component mixture A,and 13 parts component mixture B a substantially oxygen balancedexplosive is obtained. During this mixing operation also 0.3 parts of a50% sodium bichromate solution is added, which provokes a gel-likeconsistency and improved water resistancy of the explosive mixture.

EXAMPLE 2 Component mixture A In a similar way as set out in example 1 amixture of the following composition was prepared:

Parts Ammonium nitrate 40.0 Nitrate of lime, fertilizer grade 43.3Sodium nitrate 6.5 Water 6.5 Ethylene glycol 2.5 Tapioca starch 0.9 Guargum 0.3

Total 100.0

This mixture will demonstrate initial salt precipitation at about 35 C.,but may, however, be pumped at temperatures down to about 20 C. Itprovides about 235 grams of available oxygen per kilogram.

Component mixture B A viscous mixture of combustible components isprepared of the following composition:

Parts Evaporated SLllPfiiB liquor from an ammonium sulfite were addedper kilogram of the above paste. The so produced paste will consumeabout 820 grams oxygen per kilogram for complete combustion.

Preparation of the explosive When admixing 77.5 parts of componentmixture A, and 22.5 parts of component mixture B Total 100.0 parts,

a substantially oxygen balanced exposive is obtained.

Both of the here mentioned exposives will detonate completely in anabout 75 mm. diameter charge column at about C. when initiating with apentolite primer.

What is claimed is: 1. A process for producing a water-bearing exposivecomposition which comprises (a) preparing a viscous aqueous dispersioncomprising water and the oxidizing components of the explosivecomposition,

(b) preparing a viscous dispersion of the oxygen consuming components ofthe explosive composition, containing as a major component awater-soluble combustible liquid and having a viscosity substantiallythe same as that of the dispersion prepared in step a, and

(c) pumping and mixing the dispersions with each other.

2. The process of claim 1 wherein the combustible liquid is ethyleneglycol thickened with a high molecular weight compound so as to achievea viscosity substantially preventing sedimentation of the solidsubstances dispersed therein.

3. The process of claim 1 wherein the combustible liquid is molasses.

4. The process of claim 1 wherein characterized in that in the componentmixture comprising the combustible liquid is substances, an evaporatedsulfite liquor from a sulfite pulping process.

5. The process of any of claim 1 wherein very finely divided aluminum isdispersed in the combustible liquid.

6. The process of claim 1 wherein an explosive substance is dispersed inthe combustible liquid.

7. The process of claim 1 wherein at least one member selected from thegroup consisting of powdered coal, asphalt, pitch, peat, cork, bark,aluminium, magnesium, silicon and alloys of such metals is dispersed inthe combustible liquid.

8. The process of claim 1 wherein the dispersions are mixed in a mixingratio which results in a substantially oxygen balanced explosivecomposition.

9. The process of claim 6 wherein the explosive substance is trinitrotoluene.

10. The process of claim 5 wherein the aluminum is used in the form offlakes.

11. The process of claim 8 wherein the oxidizing components are thenitrates of ammonia, sodium and calcium.

References Cited UNITED STATES PATENTS 3,153,606 10/1964 Breza et al14944 X 3,160,538 12/1964 Zaslowsky et al 149--44 X 3,307,986 3/1967Grant l49'44 X 3,312,578 4/1967 Craig et al 149-44 X 3,347,722 10/1967Gordon 14944 X 3,356,544 12/1967 Fee et al 14944 X 3,377,909 4/1968Grant et al 14944 X 3,467,559 9/ 1969 Paasch et al. 149--44 3,523,048 8/1970 Hopler 149-44 X 3,617,406 11/1971 Young 149-' 60 3,619,308 11/1971Caldwell et al 149-60 STEPHEN J. LECHERT, J R., Primary Examiner US. Cl.X.R.

